> On 15 Nov 2016, at 12:22, Haravikk via swift-evolution > <[email protected]> wrote: > > >> On 15 Nov 2016, at 07:53, Rick Mann via swift-evolution >> <[email protected] <mailto:[email protected]>> wrote: >> >> >>> On Nov 14, 2016, at 22:51 , Charlie Monroe via swift-evolution >>> <[email protected] <mailto:[email protected]>> wrote: >>> >>> One major example is the NS/UITableViewDataSource or Delegate - there are >>> many many methods that you don't need to implement, hence are optional. >>> >>> But I think that this was partially solved by default implementation of >>> protocol methods, which pretty much does what you want... >> >> I just realized I only responded to someone else, and not the whole list. It >> does, but it forces me to make the return value of the protocol method >> optional, so that the default implementation can return nil. >> >> In the end, I guess that's not so bad, since I'm not happy with the entire >> approach, but it'll do for now. > > What's different about having the method return nil vs being optional? You're > attempting to call it either way, and presumably need some means of handling > the return value, except in Swift it's all nice and explicit and easy to put > in a conditional like: > > if let result = myObject.someOptionalMethod() { /* Do some stuff */ } > print(myObject.someOptionalStringMethod() ?? "") > > And so-on. If you need a method to be both optional, and return a nilable > result then you can use a double optional like so: > > if let result = myObject.someDoubleOptionalMethod() { // Method was > implemented > if let value = result { // Method returned a value > /* Do some stuff */ > } > } > > > By defining the methods as returning an Optional and throwing in default > implementations you can specify fewer, bigger protocols and make clear what > the requirements really are, though personally given the choice I'd prefer a > dozen smaller protocols that are absolutely explicit in what they do. > > But yeah, I think the tools you need are all there already; maybe there's an > argument to be made for allowing default return values on protocol methods, > to reduce the boiler-plate? > _______________________________________________ > swift-evolution mailing list > [email protected] > https://lists.swift.org/mailman/listinfo/swift-evolution
I think there is a difference between: - A method which returns an optional result, and - An optional method which, if present, always returns a result Perhaps not so much of a difference at the usage site (it’s just a question of placing a ? for optional chaining), but semantically and when conforming to the protocol, they mean different things. - Karl
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